The present invention relates to the fabrication of semiconductor-based devices. More particularly, the present invention relates to improved techniques for controlling the pressure in plasma processing chambers.
In the fabrication of semiconductor-based devices (e.g., integrated circuits, or flat panel displays) layers of material may alternately be deposited onto and etched from a substrate surface (e.g., the semiconductor wafer or the glass panel). As is well known in the art, the etching of the deposited layer(s) may be accomplished by a variety of techniques, including plasma-enhanced etching. In plasma-enhanced etching, the actual etching of the substrate takes place inside a plasma processing chamber. During etching, a plasma is formed from a suitable etchant source gas to etch areas of the substrate that are unprotected by the mask, leaving behind the desired pattern.
Among different types of plasma etching systems, those utilizing confinement rings have proven to be highly suitable for efficient production and/or for forming the ever shrinking features on the substrate. An example of such a system may be found in commonly assigned U.S. Pat. No. 5,534,751, which is incorporated by reference herein. Although the use of confinement rings results in a significant improvement in the performance of plasma processing systems, current implementations can be improved. In particular, it is realized that improvements can be made in the way in which pressure is controlled in a plasma processing system.
To facilitate discussion, FIG. 1 depicts an exemplary plasma processing chamber 100, including confinement rings 102 as they are currently implemented. Within plasma processing chamber 100, there is shown a chuck 104, representing the workpiece holder on which a substrate 106 is positioned during etching. Chuck 104 may be implemented by any suitable chucking technique, e.g., electrostatic, mechanical clamping, vacuum, or the like. During etching, RF power supply 110 may source RF power having a frequency of, for example, about 2 MHz to about 27 MHz, to chuck 104. Above substrate 106, there is disposed a reactor top 112, which supports an upper electrode 124 with an RF power supply 126. An etchant gas source 120 supplies a gas to a region within the confinement rings 102. The upper electrode 124 may be used to excite the etchant gas to a plasma and to sustain the plasma. The gas and plasma are vented to a region outside of the confinement rings 102 to an exhaust port 122.
Commonly assigned, U.S. Pat. No. 6,019,060 entitled xe2x80x9cCam-Based Arrangement For Positioning Confinement Rings In A Plasma Processing Chamberxe2x80x9d by Eric H. Lenz, issued Feb. 1, 2000, incorporated by reference taught that the pressure drop across the confinement rings is approximately proportional to the expression 1/(x2+y2+z2), where x, y, and z are the distances between confinement rings, as shown in FIG. 1. Lenz provided a single moveable confinement ring and a stationary confinement ring. By adjusting the distances between the confinement rings 102 by moving the single movable confinement ring, as taught by Lenz, a pressure control range of 17 to 30% may be obtained. With a pressure control above 30% the plasma may become unconfined due to the large gap between the rings. By controlling the pressure drop across the confinement rings the pressure within the confinement rings, the wafer area, may be controlled.
It is desirable to provide an increased control of pressure across the confinement rings.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, a plasma processing device. A vacuum chamber with an exhaust port in fluid connection with the vacuum chamber and a gas source in fluid connection with the vacuum chamber is provided. Within the vacuum chamber a confinement device for providing wafer area pressure control greater than 40% is placed.
These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.